Wednesday, 7 December 2016

Brain Activity: Is Less More?

Areas of the brain that show a decrease in activity upon learning a task (from Chein and Schneider, 2005)

Imagine an experiment where scientists are using fMRI to
look at activity in a person’s brain before and after the person learns how to do a
particular task. (The task itself doesn’t matter too much right now, but it
could be something like tapping a particular sequence of fingers, or reading
backwards, or picking out pictures of dogs hidden in a complicated landscape.) The
scientists scan the person’s brain while she is doing the task for the very
first time. Then they have the person practice doing the task until she's
really good at it. Finally, the person gets scanned again, while performing
this well-learned task. What do you think the difference will be in the
person’s brain activity? Would you expect to see more activity or less
activity?

I’ve been slogging through scientific papers that look at
changes in brain activity (using either fMRI
or PET) when we
learn skills, and growing increasingly puzzled. In some cases, when people
learn to do something, there is more activity in their brains, and the
researchers say: “See, that’s because they’re using more of their brains for
this!” But sometimes there is less activity, and the researchers conclude that
when we are good at something, our brains are more efficient.

Don’t those two things sound contradictory to you? Which is
it? Do we use less brain power or more brain power when we’re good at doing a
task? I’ve spent some time looking into this question, and when you get into
the details, the answer is… it depends.

But it does make sense, trust me.

The best explanation that I found was in The Cambridge Handbook of Expertise and Expert Performance. There’s a chapter by Nicole
Hill and Walter Schneider entitled “Brain Changes in the Development of Expertise: Neuroanatomical and
Neurophysiological Evidence about Skill-Based Adaptations”. They suggest that
when we learn a skill, there are a number of different patterns of changes in
brain activity that are seen.

One of the
most common patterns is a decrease in activity in parts of the brain that make
up the control network. These are the
parts of the brain responsible for working memory, attention, decision-making,
and sequencing steps in a task. They’re active when we perform any task that
isn’t well-learned, whether it’s a motor task, a perceptual task, or a
reasoning task. When we gain experience with a task, we don’t need to devote as
much concentration to it. We learn what steps follow which, and what is
required to efficiently get the job done. Once we’re experienced at a task, the
control network is not required to do as much work, so activity decreases in
these areas of the brain.

A second
pattern that is commonly seen is an increase in activity in parts of the brain
specifically related to performing the task. For a motor task such as a
sequence of finger taps, there is an increase in activity in the primary motor
cortex of the brain (as shown by Avi Karni and colleagues in 1995). This is
believed to be due to the recruitment of more neurons into the representation
of the movement and supports the idea that networks of neurons in the primary
motor cortex can code for sequences of movements. So when musicians are playing,
there is a larger part of the primary motor cortex that is active, causing their hands to move
in well-learned sequences.

A third
pattern is known as functional reorganization, in which different areas of the
brain are seen to be active when comparing novices vs. experts. For instance, in
motor learning tasks such as learning a sequence of key-presses, when we
initially are trying to learn the sequence, there is a lot of activity in the
cerebellum, but once the sequence is well-learned, the cerebellum is much less active. Instead, there is an increase in activity in the
striatum, a part of the brain believed to be responsible for (among other
things) sequences of movements. Julien Doyon and colleagues, who reported this in 2002, conclude that the cerebellum has an important role in learning a motor task, but much less of a role in performing the task once it is well-learned.

All three
patterns can be seen when learning different aspects of music, depending on
what the learning task is. And sometimes all three patterns occur at the same
time, so that we see a decrease in activity in control regions of the brain, an increase in
regions specifically related to a task, and also some transfer of activity to
regions that are not initially active. This is part of why it is so difficult to interpret data
about activity in the brain. Understanding what each region of the brain does
in relation to the task at hand allows us to tease apart the differences we see.
And conversely, seeing how the activity changes in a particular area of the
brain helps us understand how it contributes to learning and to performance of
a skilled task.

About Me

Tara Gaertner is a neuroscientist, music educator, writer and speaker. She holds a Bachelor’s degree in Music from McGill University and a Ph.D. in Neuroscience from the University of Texas, Houston. She has taught piano, flute, and music theory since 1988 and currently teaches the Music for Young Children program as well as private piano and flute lessons. She is an Adjunct Professor at the University of British Columbia, lecturing on Neuroscience in the department of Occupational Science and Occupational Therapy.